S. Simov

Morphology of hollow crystals of II–VI compounds

Published data on hollow crystals of II–VI compounds are reviewed. The experimental conditions for obtaining hollow crystals are discussed and presented systematically in tables. Some inferences concerning the effect of impurities, supersaturation, type of substrate and other factors on the growth of hollow crystals are made. Particular attention is paid to the structure, form and defects of hollow crystals and it is established that they can be classified in the following groups: hollow hexagonal columns and prisms, hollow pyramids, hollow crystals with spiral-like hexagonal form and hollow crystals with a more complex structure consisting of whisker-pyramid-prism. The mechanism and kinetics of the growth of hollow crystals as presented by different authors are discussed.

Dependence of glow discharge Si:H:Cl film morphology on diluent gas and SiCl4 partial pressure

TEM, THEED and field-assisted silver ion exchange have been employed to study the glow discharge (GD) Si∶H∶Cl films deposited from SiH4-SiCl4 gas mixtures. The character of the THEED patterns shows that the films are rather amorphous, and that their structure does not alter with the change in the gas mixture. The honeycomb-like morphology of the films is strongly affected by the type of gas in which SiH4 is diluted (Ar or H2). An increase in the SiCl4 partial pressure leads to the uniformity and to the decrease of the island dimension only for the films deposited from SiH4(H2)-SiCl4. A possible correlation between the film morphology and the micropore density is proposed.

Structural peculiarities in high-dose Ar+ implanted silicon

Abstract The effect of 65 keV high-dose Ar + implantation (5.10 15 ions cm −2 ) in single-crystalline silicon is studied by means of TEM, THEED and HREM techniques. It is established that crystalline structures in the amorphized layer are created, with orientations different from that of the nondamaged matrix. It is supposed that the crystallization process is associated with the energy transfer due to the radiation.

Growth and morphology of cadmium oxide whiskers

A way of growing cadmium oxide whiskers is described. The whiskers were grown on CdS single crystal substrates having a palladium film (d ∼ 10 to 30 nm) deposited on the surface, upon annealing of the samples in an argon atmosphere with small oxygen impurity, at temperatures 580 to 640° C, for 2 to 4 H. The whiskers have micron sizes: a cross-section of several square micrometres, length from several tens to several hundreds of micrometres. The composition (CdO) and structure of the whiskers have been determined by X-ray microanalysis and reflection high energy electron diffraction. The main crystal forms studied by SEM, are described: tetragonal prisms, needles, threads, prisms with a faceted formation on the upper base, plates. On the basis of the data from electron diffraction and SEM as well as the comparison with literature data, it is established that the predominant orientation of growth is 〈1 00〉.

Effects of high dose Bi+ implantation on Si : An atomic force and transmission electron microscopy study

Abstract The effect of bismuth ion implantation (dose range 10 15 –10 18 cm −2 ) on the surface morphology of monocrystalline silicon was investigated by Atomic Force Microscopy (AFM) and Cross-Sectional Transmission Electron Microscopy (XTEM) and the data obtained compared. The low levels of roughness observed at dose interval 10 15 –6×10 15 cm −2 could be related to an amorphous layer created at the target surface. Roughness increased at a dose of 8×10 15 cm −2 , where drastic changes in the morphology of the amorphous layer began, i.e. with nonepitaxial recrystallization of Si and simultaneous agglomeration of Bi in nanocrystals. The maximum surface roughness at a dose 1×10 18 cm −2 was related to the specific erosion of the surface in the form of hillocks connected to the extremely large value of the sputtering yield of Bi (61.8 at. i. −1 ) in comparison with the sputtering yield of Si (3 at. i. −1 ).

Study of the morphology of CdTe whiskers by scanning electron microscope

Abstract CdTe whiskers grown on substrates of (0001)CdS, as well as (100) and (111)Ge have been studied with a scanning electron microscope. The morphology of these whiskers, in the form of hexagonal prisms, was studied and the transitions from one to another form of prismatic or pyramidal walls are reported. Some less frequent forms of whiskers such as needles and triplets are also shown.

Observations of hollow cadmium telluride crystals with a scanning electron microscope

Abstract CdTe layers are obtained upon substrates from (111) Ge and (0001) CdS with a thickness of 30–40 μm. The hollow crystals, observed upon those layers, are studied with a scanning electron microscope in the regime of secondary electron emission. Electron photomicrographs were taken of separate crystals, as well as of some of their details. The CdTe layer surface is completely covered with hollow crystals, whose density reaches sometimes 1.5 × 103 cm-2. The hollow crystals observed are composed of a whisker-needle with a transition into a cone (pyramid), terminating with a hexahedral prism. Hollow crystals with an “open” and a “closed” lateral surface are observed. The appearance of new planes upon the upper surface of the hollow crystals is an interesting peculiarity, the planes blunting the edges, which might be the transition to the closing of the hollow crystals. An attempt was made for a partial explanation of the growth mechanism of the described CdTe hollow crystals.

Observations on whiskers and skeletal crystals in PbSe layers by scanning electron microscopy

Whiskers and skeletal crystals of PbSe are obtained on substrates of (100) germanium. The production conditions and peculiarities of their structures are discussed. SEM observations show that the whiskers are prism-shaped possessing rectangular or square cross-sections with lengths up to 190μm and widths of the surrounding walls up to 26μm. Hollow pyramidal crystals with their apexes connected to the layer surface by a whisker are described, as well as hollow crystals with an open or a closed surrounding surface. Certain aspects of the growth mechanism of skeletal crystals and whiskers are discussed.

Thermal regrowth of silicon after high-dose Ar+ implantation

Abstract By means of RHEED it is found that a thermal annealing even at 1000°C of high-dose (5 × 1015 ions/cm2) Ar+-implanted 〈111〉 silicon does not lead to complete regrowth of the damaged layer. On the basis of some peculiarities of the damaged layer in as-implanted samples, revealed by TEM and HREM—namely, the existence of spherical cavities with crystalline interface regions—a reasonable explanation of the established incomplete recovery is proposed.

Structural study of glow discharge a — Si ∶ H films

Structural properties of a-Si:H films deposited on single crystalline silicon substrates have been studied by means of TEM, THEED, RHEED, and RDF. It is concluded that there are microcrystallites embedded in the amorphous phase which has a homogeneous structure. The atomic bonding configuration in the amorphous phase is discussed.